Groundwater quality in arid and semi-arid regions is under increasing pressure from
both natural and anthropogenic sources. This study presents a comprehensive assessment
of groundwater quality in the Gonbad Plain, Iran, to determine its suitability for
drinking and to identify the controlling hydrogeochemical processes. A total of 45
groundwater samples were analyzed for their physicochemical parameters, and the data
were evaluated using an integrated approach combining hydrochemical facies analysis,
geochemical modeling (PHREEQC), multivariate statistical techniques (Principal component
analysis (PCA) and hierarchal cluster analysis (HCA)), and human health risk assessment
(Heavy metal pollution index (HPI), Hazard quotient (HQ), Hazard index (HI)). The
results reveal a hydrochemical evolution from fresh Ca-HCO₃ type water to saline Na-Cl
type water, primarily controlled by three key mechanisms: (1) dissolution of evaporite
minerals (halite and gypsum), (2) cation exchange, and (3) evaporation. The Gibbs
diagrams confirmed that rock-water interaction and evaporation are the dominant processes
governing water chemistry. Iron concentrations varied from 0.01 mg/L to 4.12 mg/L,
with a mean of 0.46 mg/L and a standard deviation of 0.66 mg/L. The median iron concentration
was 0.27 mg/L. Manganese concentrations ranged from 0.015 mg/L to 0.47 mg/L, with
a mean of 0.09 mg/L and a standard deviation of 0.07 mg/L. The median manganese concentration
was 0.08 mg/L. The HPI indicated a critical water quality crisis, with 77.8% of the
samples being unsuitable for drinking (HPI > 100), primarily due to elevated concentrations
of manganese. The non-carcinogenic health risk assessment revealed that while the
dermal exposure pathway poses no significant risk, oral ingestion of groundwater presents
a potential health hazard, particularly for children. The HI exceeded the safe limit
of 1.0 in 11.1% of the samples for children, with manganese being the primary contributor
to the risk. This is the first study apply integrated framework that combines multivariate
statistics, geochemical modeling, and health risk indices to evaluate groundwater
vulnerability in Gonbad-e Kavus. The study’s alignment with UN Sustainable Development
Goal 6 (Clean Water and Sanitation).
